Research On 3D Microsurface Profile Measurement Technology Based On White-Light Interference Principle

For MEMS(Micro-Electro-Mechanical System) characterization, a vertical scanning white-light interferometric measurement system, which has the characteristics of long-work-distance, fast, non-contact and full field measurement, has been developed to address the growing demand for static and dynamic characterization of MEMS devices. The main contents of this thesis comprise the following aspects:Based on a novel LED collimation method, a vertical scanning white-light interferometry surface profiler is designed. The coherence length of light source, system's resolution and CCD resolution are analyzed.The main white-light interference processing algorithm is introduced, particularly, the phase-shifting algorithm and SEST(Square-envelop function Estimation by Sampling Theory) algorithm based on sampling theory is studied deeply. A method using a circular buffer to locate interference region is proposed based on SEST algorithm, which reduce the number of sampling data and computational cost, increased data processing speed. The algorithm of phase-shifting and SEST is simulated by computer; the results show that the spectral width of light source has great impact to the accuracy. The accuracy of phase-shifting algorithm is higher than that of SEST algorithm under the same condition, but the measurement speed is lower because of the narrow sampling interval.A vertical scanning white-light interferometry surface profiler has been developed, which capable of operate in the PSI(Phase-Shifting Interferometry) mode and VSI(Vertical Scanning Interferometry) mode. The software of system is developed in the VC++6.0 integrated development environment, the algorithm of three-step phase-shifting, five-step phase-shifting and SEST is also achieved in this environment. An effective file format is proposed to store the three-dimensional surface profile data. The standard step height of VEECO Corp. is measured using this system, the experimental results, which is attained using different processing algorithm described above, is compared and analyzed. The results indicate that the vertical resolution of system is rather high.